Modeling Viral and Marketing Growth, Part 3 of 3

This is a question I should have answered before I even started down this road.

To be honest, I did it primarily as a challenge - to stretch my brain a little bit. If I were faced with this exact same task in my daily work, undoubtedly I would just use normal Excel formulas. In some ways, this modeling exercise has been a deliberate misuse of PowerPivot. A handful of parameters with no source data whatsoever - this is NOT what the PowerPivot engine was built for, which explains why the PowerPivot solution is actually significantly more difficult than the Excel solution.